Distance measuring device



Feb. 2, 1954 P, A, PERiLHQU 2,658,288

DISTANCE MEASURING DEVICE Filed sept. 22, 1948 5 sheds-sheet 1 s/Iu I by Y' P. A. PERILHOU DISTANCE:I MEASURING DEVICE Feb. 2, 1954 5 Sheets-Sheet 2 Filed Sept. 22, 1948 wl/www.

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5 Sheets-Sheet 3 l 6 057.3 ,SWR1 il Feb. 2, 1954 P. A. PERILHOU DISTANCE MEASURING DEVICE 5 Sheets-Sheet 4 Filed Sept. 22, 1948 by www rfi/0M Feb, 2, 1954 P. A. PERILHOU 2,668,288

DISTANCE MEASURING DEVICE Filed Sept. 22. 1948 5 Sheets-Sheet 5 a7? v .05X l Patented Feb. 2, 195.4e

DISTANCE MEASURING DEVICE Pierre Andr Perilhou, Clamart, France, assigner to Office National dEtudes et de Recherches Aeronautiques, Paris, France, a company of France Application September 22, 1948, Serial N o. 50,515

Claims priority, application France September 23, 1947 21 Claims.

This invention relates to distance measuring equipment and more particularly to systems permitting to determine a distance between two points with the aid of radiant or wave energy.

An object of the invention is to provide a novel method and means for distance measurement based on the use of radiant or wave energy which is caused to be transmitted from one point and is caused to be received at another point, on at least two spaced and independent aerials and in which the eifects of reception of said energy by said aerials are used for giving a desired measure of distance.

More particularly, the invention has for its object a novel method for distance measurement or determination which method consists in producing at a location and namely the one'with respect to which a distance is to be determined, wave energy radiations presenting a characteristic variable with -distance when received at two spaced points, in receiving said radiations at another location and namely the one the spacing of which with respect to the rst location is to be determined on at least two spaced and independent receiving aerials and in using the signals thus received by said two aerials to show a variation of said variable characteristic of said radiations as the same are received by .one and the other of said aerials.

Another object of the invention is to provide a novel method for distance measurement or determination which consists in producing at a 1ocation and namely the one with respect to which a distance is to be determined, wave energy radiations presenting a characteristic variable with time, in receiving said radiations at another location and namely the one, the spacing of which with respect to the first location is to bevdetermined, on at least two spaced'and independent receiving aerials and in using the signals thus received by said aerials so as to show a variation of said variable characteristic of said radiations depending on the reception of said radiations by one and the other of said aerials.

Another object of the invention is to provide a method and system rfor distance measurement of the type specified above in which the signals received by the receiving aerials are compared in relation to time to produce a desired indication of distance.

' Another object of the invention is to provide a method and system for distance measurement of thetype specified above in which thesignals re-j ceived by the receiving aerials are combined to produce a desired indication of distance.

vide a novel method and means of the kind specified above making use of ultrashort or very high frequency radiations for which the spacing between the receiving aerials is relatively great in comparison with the wavelength of said radi--` ations.

A more particular object of the invention concerns the application of the specified method to navigation of -dirigible crafts whether aerial or naval, in which two receiving aerials form a part of distance measuring equipment carried by the craft and constitute on said craft a distance measuring base line permitting to determine the distance of the craft with respect to a desiredi point provided with a radiant energy transmit ting equipment adapted to produce a rotating beam of radiant energy.

A still further object of the invention concerns a particular embodiment of the speciiied method and system comprising the use of a rotating beam of radiant energy located at one point and Vof two independent receiving aerials spaced apart and forming a distance measuring base line at another point, these receiving aerials being associated with one or two suitable receivers permitting to compare in relation to time two equivalent phases of reception of the rotating beam by each of said aerials.

The invention contemplates furthermore another variation of the specified method permitting to obtain a measure of distance, for instance between a rotating radio beacon or the like and a dlrigible craft independently of the orientation. of the distance measuring base line carried by -thef craft with respect to the direction joining the point of location of said craft with the point of location of the radio beacon.

In this particular embodiment of the invention, the dirigible craft is provided according to the invention with four receiving aerials located at the extremities of two distance measuring base lines at right angles andthe measure of distance is obtained by combining. the effects Vof reception of said four aerials taken by pairs.

In accordance with a particular feature of the invention, the measure of distance in the above last mentioned case is obtained by measuring the angles of parallax with respect to the point to which theddista'ncjel is to be measured, of the two distance measuring base lines at right angles constituted by four aerials taken two by two, this Y measure being expressed in values of electrical voltages which are combined thereafterfior-giving the angle of parallax fora base, line` of the same length placed at thefV considered point of reception, perpendicularly to the line passing through said point and the point of transmission of radiant energy.

A still further object of the invention is to provide a system of distance measurement' operating in accordance with the method of the type speci-` fied, in which means are provided permitting to render a current or voltage used for indication, variable with distance in'such a manner that this current orvoltage passesV through a zero value for. apredeterininate distance to a transmitter andnafnely.atransmitter of. a rotating beam of radiant energy, which distance. in case. of applicatign, of the. .invention to the blind landing of aircraft may bethe .distance corresponding to a desired, point on. a runway whereby any possibi-e misadjustment or troubleinthe circuits of direct current: used insuch a system may be eliminated.

Another object of the invention is to provide al system; of1 distance measurement of the type refg-nredl to above in which the indicating cur rent ,is made variable.k with distance according toga hyperbolic relation such that this current talgegatthe limit, withthe-distance increasing infinitely, .a finite and predetermined value.

This latter object of the invention is attained by. .usir1gA the. signal producedby one of the receiving` aerials fortriggering a multivibrator producingasignal, of. a. rectangular form the durae tioncof Vwhich corresponds to the time interval requiredifor. therotating beam to pass from one to.the.other..of the two aerials at a predeterminate, distancaby.. deriving from said rectangulansignal a pulseV corresponding to its rear or trailing edge and byl causing said pulse to act simultaneouslywith the signal produced by the other aerial upon an Eccles-Jordan network whereby theoutput current of the assembly is giveniaforr'n variable as a function of the distanceor-an averagev voltage defined by the relation D-l e-aX D Y in whichvD isthedistance between the receivingbase line formed by, two aerials and the transmitter `l is the distance for which the current tales a vZero value and ais the coefficient which determines the value of the current at the limit, when'` D increases innitely.

Another object of the invention concerns the provision of `a novel method and system for measuring a distance between two points comprising the use at one of said points of two transmitting aerials producing synchronously yrelated variable characteristic radiations and. at the other point, two spaced and independent receiving aerials forming, as previously mentioned, a distance measuring base line and in which said measurefof distance is obtainedby combining thedifferences of said variable characteristic (5f-transmitted radiations as the same are re,- ceivedby each receiving aerial fromboth transmitters simultaneously, each of said variable characteristic differences being a function of the distance of said transmitting aerials to the middle point of the receiving base line formed by said receiving aerials, when thisV base line is oriented perpe-ndicularly and is symmetrical to the central axis of the transmitting base line formed by said two transmitters or transmitting aerials.

According to another feature of the invention, there is provided a novel method and system for measuring a distance between two points comprislg tile use` at one of said points of two transrnittingV aerials producing synchronously related frequency modulated radiations and at another point, two spaced and electrically independent receiving aerials forming, as previously mentirmed,Y adistance measuring base line and in whichsaid measure of distance is obtained by a summation of differences of frequencies received simultaneously by each,.aerial from both transmitters, each of said frequency differences being a function of the distance ofthe transmitting aerials to the middle point of the receivingbase line formed' by said two receiving aerialswhen this line is oriented perpendicularly to, andnis placed symmetrically with respect to thecentral axis of the transmitting base line formed 'by the. two transmitting aerials.

The invention as dened in the two precedingi paragraphs is preferably reduced to practice 4by, the use of ultra-short or very high frequency radiations for which the spacing between, two receiving aeriais is relatively great when compared to the wave length.ofsaid.radiations. Also, in this case, it is applicablemoreparticularly to:v navigation of dirigibleV crafts, such as air or marine crafts.

The above andother object andfeaturesof, the inventionwillappear more fully hereinafter from. the following detailed description andthe accom?` panying drawings showing by way ofexample certain preferredl embodimentsrof the invention` it being understood thatA these drawings are given` for the purpose'of illustration only and arenot to be considered as limiting inY any way. this; invention. Y

On these drawings;

Fig. 1 is a schematic representation. of the embodiment of the method according. to them-- vention applied. tok the-measure ofay distance between a dirigiblecraftsuch as anaircraftfjand,- a point of its destination -whichfmay beprovidedi: with a rotating radio beacon'.

Fig. 2 shows acurveofvariationinrelation to timerof a voltage induceddn a. receiving aeriabw by the passage of a rotating. beam,y of radiantienergy through the point of location ofVV saldi` aerial.

Fig. 3 showson a sameftimeA base; two signa-l; voltage: curvesinduced in; two spaced receiving; aerials as well as corresponding-locallyproduced-. pulsesfor defining in relationto .timethe rela.- tive position of `said signal voltages.-`-

Fig. 4 shows ablcokv diagramo aydistance; measuring apparatus-or` equipment which; may be used in asystemaccordingtol'igi l.-

Fig-.- 4a. shows a block diagram;4 of;v ag;mcdiiicaf tionof the distance -rneasuring3,apparatusy show-nn in Fig. 4.

Fig. 5 shows a front view of an oscilloscope` which maybe4 usedinthe equipment according to Fig` fand 4illustrates thelmzyonnerin whichrthe indication of .distance may.be;p r9d llid Oia-suchY an indicator.

Fig. 6 shows anotherfembcdimentmf f distance measuring apparatus adapted for use with a rotating. beam of radiant energy and which permits to obtain a zero indication for a predetermined distance from the point of origin of said beam. Y Y,

Fig. 7 is a schematic representation illustrating the use of a system of four receiving aerials forming two receiving base lines at right angles permitting to determine the distance between a point of origin of a rotating beam of radiant energy and lsaid receiving system, independently of the orientation of said system with respect to a line joining the center of said system to the point of origin of the rotating beam.

Fig. 8 shows a schematic representation illustrating the operation of another arrangement of four receiving aerials permitting to obtain a result similar to that of Fig. 7. Y K

Fig. 9 is a block diagram of a distance measuring apparatus which may be used with an antenna arrangement according to Figs. '7 or 8.

Fig. l is a diagram given for the purpose of illustration of another embodiment of the method according to the invention comprising the use at one point of two transmitting aerials producing frequency modulated rediations and at the other point two receiving aerials.

Fig. l1 is a diagram showing the frequency modulation applied to the two transmitting aerials of a system according to Fig. l0.

Fig. 12 is a diagram given for the explanation of the operation of said last embodiment of the invention.

Fig. 13 is a schematic representation of the application of the embodiment of the invention to the navigation of a dirigible craft such as an aircraft toward a point of destination.

Fig. 14 is a block diagram of a distance measuring apparatus which may be used in said last embodiment of the invention.

Referring now to the drawings for a detailed description of the invention, it will be noted that Figs. l to relate to the rst embodiment of the method according to the invention. As shown in Fig. 1 there is provided at point O which may be for instance a point of destination of an aircraft l, an ultra high frequency transmitter feeding a directive aerial of high concentration (not indicated). This aerial may be constituted by a pavillon, a parabolic mirror or a cylindricaparabolic reiector, etc. The horizontal directivity of such an aerial will be preferably as great as possible, i. e. the aerial should be rela.- tively wide. In thevertical plane, the directivity of this aerial will be less pronounced especially in the case of application of the method according to the invention to the navigation of aircrafts such as airplanes for instance, this for the purpose of reaching aircrafts at very different heights.

The angle of opening or divergency of the beam produced by such an aerial, whichmay be supposed for the purpose of explanation, to be free from lateral lobes, is indicated on Fig. 1 by 0 and will be expressed in degrees. With very short waves, this angle may have a value of a few degrees. This aerial is rotated about a vertical axis passing through point Oat a uniform angular speed w. Accordingly, the space around said point O is regularly swept by the beam of electro-magnetic radiations. When the beam in its rotation passes through the point of location of a receiving aerial such as A, an electromotive force is induced in said aerial and the variation of saidelectro-motive force in relation to time, is determined by the form of the directivity curve of the transmitting aerial. Such a curve is indicated by way of example on Fig. 2.

If there is provided then a second receiver, the aerial of which is located at point B, such that point O is equally spaced from point A and from point B and that the angle AOB has a certain value e, the envelops of electromotive forces induced in aerials A and B will be represented by two identical curves such as shown in Fig. 3 and which are shifted one from the other in relation to time by a time distance If distance AB is known, it is possible to derive from a diagram in which said two envelops curves are plotted against a time base asA shown in Fig. 3, the distance D between the receiving base line AB and point O.

In practice, aerials A and B may be provided at the opposite extremities of the wings of an aircraft whereby the same may be oriented following the direction toward the radio beacon O, for instance, by manoeuvring so as to obtain a maximum spacing between the signal received by aerials A and B, or by any other means provided to permit its navigation or orientation for instance during a landing.

The measure of the time lag between the curves of voltages received by the two aerials may be effected by any known method and means and in particular by projecting said curves on a screen of an oscilloscope. The sharpness of the definition may be increased by using the method claimed and described in the copending application Serial No. 48,487, filed on September 9, 1948, according to which each of such signal curves may be positionedV in relation to time by a locally produced sharply defined pulse corresponding to a predetermined point of said signal curve having a predetermined relation to the maximum amplitude of the same.

The described system requires the use of two separate receivers for signals received by each aerial. Fig. 4 of the drawing shows a block diagram of an equipment which may be used for this purpose. As shown in said iigure, this equipment comprises two aerials which may be constituted for instance, by di-poles 2 and 2', each followed by a receiver which may comprise a detector and an amplifier indicated schematically together by a single reference numeral 3, 3' respectively and a puiser d, 'i'. The outputs of pulsers d and d ofthe two receivers are connected to the input of a mixer 5 followed by an Eccles-Jordan network d and a filter l,^this latter being connected to a galvanometric instrument with a single coil 8, the deviation of which gives the desired measure of distance.

Instead of using a pointer instrument as described hereinabove it is possible also to use a cathode ray tube or oscilloscope I0. This embodiment is shown in Fig. 4d. In this latter case, the first received signal, that is one coming from the aerial which is iirst touched by the rotating beam, may be used for controlling the triggering of a time base device H controlling the horizonta1 scanning system l 2 ofsuch an oscilloscope whilst the signal coming from the other antenna is adapted to control the cathode ray vertical deiiection device I3 of the same.

Fig. 5 shows a front view of screen I4 of such an oscilloscope which thus forms a distance indicating dial according to the invention. As shown, screen I4 is provided following its hori- 9 cated at 28 and which is followed by a filter 29 and a measuring apparatus 30. With an arrangement such as described above, the law of variation of the output current feeding indicator 3b as a function of the distance is of a hyperbolic form defined by the equation D-D1 D It will be noted that this current for D=D1 is equal to zero and at the limit when D increases innitely it becomes equal to coeicient a.

From the above description, it isapparent that the invention provides thus a method whereby a dirigible craft such as an aircraft may determine 'its distance to a desired point, from which is transmitted a rotating beam of radiant energy, while flying toward said point or in other words, while the distance measuring base line is oriented perpendicularly and is arranged symmetrically with respect to a straight line joining the middle point of said base line to the point of origin of the rotating beam of radiant energy. Thus, the measure of a distance according to said method involves a predetermined orientation of the base line and consequently of a dirigible craft carrying the same with respect to a point in relation to which said distance is to be determined.

However, in certain instances, it may be interesting to obtain a desired indication of distance independently of a predetermined orientation of the receiving or distance measuring base line.

Accordingly the present invention concerns also an improvement of the method of distance measurement described above whereby the measure of distance between two points may be effected thus independently of the orientation of said receiving or distance measuring .base line. According to this aspect of the invention, it is suggested to use at a point of reception two receiving or distance measuring base lines arranged at right angles, one to the other and each comprising two receiving aerials spaced apart and independent one from the other and to combine the effects or reception of these two systems to determine a desired measure of distance. More particularly this modied method, according to the invention, consists in measuring the angles of parallax'or angles under which one sees, from theY point with respect to which the distance is to be measured, the two receiving base lines formed respectively by two pairs of receiving aerials, the measures of said angles being expressed in values of electrical voltages which are combined then to determine a parallax angle of a base line of the same length placed at the same point perpendicularly to the direction passing through said points of transmission and reception.

Referring now to Figure 7 of the drawings, there are shown four receiving aerials A, B, C, and D located at the corners of a square having its center located at point M spaced by a distance D from a point of origin O, of a rotating beam of wave energy.

The angle of parallax corresponding to a single receiving or distance measuring base line suitably oriented with respect to direction OM as shown in Figure l. will be indicated by e. Then, the angles of parallax corresponding to two receiving base lines formed by two pairs of aerials AB and CD as shown on Figure "l, will be indicated by e, and e, respectively, these base lines being deviated by an angle a withk respect t a position in which one of said base lines and namely base line AB is perpendicular to said direction OM.

e 1 d cos a and il d sin a It appears thus that by knowing angles e, and e2, it is possible to determine angle e giving the measure of a distance in accordance with the equation:

e k D where lc is a coefcient of proportionality.

According to the invention angles e, and e, are determined by following the method previously described, by measuring the time interval elaps-l ing between two pulses obtained by respective passages of the rotating beam by the two aerials of each receiving base line. The indications corresponding to each base line are translated by a time measuring device known per se, into continuous current voltages capable of determining a current output proportional to values e, and e2. In order to -obtain e, it is possible for instance. to use two coils arrangedatright angles and respectively traversed by currents proportional to Values e, and e, and by providing inside of `said coils and in inductive relation therewith a third or search coil adapted-torotate at a constant speed by a driving motor. This search coil receives by induction a voitage the tip value of which is proportional to angle e.

t is possible naturally to have a different length for each receiving base, that is to have AB=d dierent from BC=Z as shown in Figure 3. In such a case, the signals produced by the receiving base BC will have to be multiplied by a quantity before the same are combined with those of the other base AB.

Fig. 9 of the drawings shows a schematic block diagram of an apparatus or equipment which may be used for reducing to practice the above mentioned method of distance measurement.

Each receiving'aerial 3 l, 35, 4I and 46 is associated with a suitable series of apparatus comprising respectively a resonant volume 32, 31, 42, and 4l, an amplier 33, 38, 43 and 48, a limiter arrangement 3d, 39, @d and e9, a dilerentiator arrangement 35, di), i5 and 53. The two channels corresponding respectively to aerials 3l and 35 and the two channels corresponding respectively to aerials @E and i5 are connected by pairs at their outputs, to two mixers 5| and 54 followed by puiser arrangements 52 and 55 each producing a signal. of a duration equal to the time interval between the pulses produced by successive passages of the rotating beam, by two aerials co1'- responding to each receiving base line and two `13 It is possible thus to establish the following table showing the correspondence between factor K and distance D.

Distance Per Frequencies cent D= factor K Fig. 14 shows a block diagram of a distance measuring equipment which may be used for producing a visual and direct indication of a distance based on the above described method.

As shown in said ngure, this equipment comprises two aerials corresponding to aerials A and B which may be constituted for instance by dipoles 62 and c2. Each of said aerials is followed by a receiver which may comprise for instance a detector 53, $3', an amplifier ci, 64 and a discriminator 65, t5. The outputs of said discriminators 65, 65' are respectively connected to two coils 66, 6l of a cross coil galvanometric indicator giving a deviation proportional to the sum of received signals, which as explained hereinabove represents with a constant factor taken into account and according to the table of correspondence indicated above, a distance between the receiving base line carried in the present instance, by an aircraft and the base line of the two transmitting aerials which may denne the point of Ylanding of the craft. The indications of distance may be produced thus directly by a needle moving over a dial graduated in units of distance.

The invention provides thus an improved method and system of distance measurement making use of a receiving distance measuring equipment comprising two aerials the effects of which are combined or compared to produce a desired indication of distance. Although several embodiments permitting to reduce to practice said method have been described and illustrated, it is to be understood that the invention is not limited to said specic embodiments but may be reproduced or applied in a different manner evident to men skilled in the art without departing from the spirit of the invention.

What is claimed is:

l. A system for distance measurement comprising means for transmitting from one location wave energy radiations presenting in azimuth a variable characteristic and means for receiving said radiations at another location for providing an indication of distance between said two loca tions, said latter means comprising at least two independent aerials spaced apart transversely to the direction joining said locations and means using the signals received by said two aerials to provide said indication by the difference in value of said variable characteristic of said radiations as the same are received by one and the other of said aerials.

2. A system for distance measurement comprising means for transmitting from one location wave energy radiations presenting in azimuth a characteristic variable with time and means for receiving said radiations at another location for providing a measure of distance be tween said two locations, said latter means com prising at least two independent aerials spaced apart transversely to the direction joining said locations and means using the signals received by said two aerials to provide said measure by the diierence in value of said variable characteristic of said radiations as the same are received by one and the other of said aerials.

3. A system according to claim 2 comprising means for comparing in relation to time the effects of reception of said aerials to produce a measure of distance between said points.

4. A system for distance measurement comprising means for transmitting from one point a beam of radiant energy adapted to rotate in azin muth and means for receiving said beam at another point to provide an indication of distance between said two points, said latter means comprising at least two lindependent aerials spaced apart transversely to the direction joining said points and means for comparing in relation to time the equivalent instants of reception of said rotating beam by said aerials so as topprovide an indication of distance as a function of time spacing of said instants of reception.

5. A system for distance measurement comprising means for transmitting from one point a beam of radiant energy adapted to rotate in azimuth and means for receiving said beam at another point to provide an indication of distance between said two points, said latter means comprising at least two independent aerials spaced apart transversely to the direction joining said points and means for combining the effects of reception of said beam by said aerials so as to provide an indication of distance by a value of a current or voltage dependent on the time spacing of equivalent instants of said effects of reception.

6. A system for distance measurement according to claim 4 comprising a cathode ray tube oscilloscope for comparing in relation to time the effects of reception of the two aerials.

7. A system for distance measurement accord. ing to claim 4 in which means for comparing in relation to time the effects of reception of the two aerials comprise a cathode ray tube oscilloscope having two cathode ray deflecting devices arranged at a right angle, a time base device adapted to control one of said deflecting devices, means for triggering said time base device by a signal produced by one of the aerials and means for controlling the other of said deecting devices by a signal produced by the other of said aerials.

8. A system for distance measurement accord ing to claim 4 in which means for comparing in relation to time the effects of reception of the two aerials comprise a cathode ray tube oscilloscope having horizontal and a vertical deflecting devices, a time base device adapted to control said horizontal deflecting device, means for triggering said time base device by a signal pro duced by one of the aerials and means for controlling the vertical deflecting device by a signal produced by the other of said aerials.

9. A system for distance measurement comprising means for transmitting from one point a beam of radiant energy adapted to rotate in azimuth and means for receiving said beam at another point to provide an indication of distance between said two points, said latter means comprising at least two independent aerials spaced apart transversely to the direction join ing said points, means for indexing in relation to time signal curves of reception of said beam by said aerials, by locally produced sharply defined pulses corresponding to a point on said curves 7a determined by a certain level of said signals, havdecenas 15 114g a predetermined relation to the maximum level thereof and means for comparing in relation to time said locally produced pulses so as to provide an indication Vof distance by the time spacing of said pulses.

A10. A system Vfor distance measurement comprising means for transmitting from one point a beam of radiant energy adapted to rotate in azimuth and means for receiving said beam at another point to provide an indication of distance between said two points, said `latter means comprising at least two spaced and independent aerials, means for indexing in relation 'to time signal curves of reception of said beam by said aerials by locally produced sharply dei-ined pulses, corresponding to a point on said curves determined by a certain level of said signals, having a predetermined relation to the maximum level thereof and means for combining said localh7 produced pulses so as to provide an indication or measure of distance by the value of a current or voltage dependent on the time spacing of said pulses.

11. A system for distance measurement according to claim 9 comprising a cathode ray tube oscilloscope for comparing in relation to time said locally produced pulses.

12. A system .for distance measurement according to claim 5 comprising means for detecting,

amplifying and transforming signals induced in u each aerial into pulses of short duration, time spaced one from the other proportionally to the distance between the point of location of the receiving aerials and the point of origin of the rotating beam, means for combining said spaced pulses into a current or voltage proportional to their spacing in time and means for measuring said current or voltage.

13. A system for distance measurement according to claim 5 comprising means for combining the eiects of reception of the two aerials including means rendering said indicating current or voltage variable with distance so that said distance indication passes through a zero value at a predetermined distance between the transmitting and receiving points when one of said points moves toward the other.

14. A system for distance measurement according to claim 5 in which means for combining the eiects of reception of the two aerials include means rendering said indicating current or voltl age variable with distance according to a hyperbolic relation whereby said current or voltage takes at a limit with the distance increasing infinitely a vrlnite and a predetermined value.

l5. A system for distance measurement between two points one of which is movable toward theV other, comprising at one point means for producing a beam of radiant energy adapted to rotate ,in azimuth and means for receiving said beam at the other point, said latter means comprising at least two independent aerials spaced apart transversely to the direction joining said points, receiver means associated with each of said aerials a multivibrator adapted to be triggered by the signal from one of the aerials for producing a signal of a rectangular form of ay duration corresponding to the time interval required for the beam to pass Yfrom one to the other aerial at a predetermined distance, means or deriving vfrom said rectangular signal a pulse corresponding to its trailing edge, an Eccles- Jordan circuit means for causing said pulse together with a signal from the other aerial to act on said Eccles-Jordan network and means for 3.6 measuring the outputcurrent `of said latter network.

16. A system for 'distance measurement comprising means for transmitting from one point radiant or wave energy presenting in azimuth a variable characteristic and means for receiving said energy at another point to provide an indication of 'distance 'between said points, said latter means comprising four independent aerials and means combining the effects of reception of said aerials to provide said indication of distance independently of the lorientation of the receiving base formed by said aerials with respect to the direction joining the two distant points.

17. A system for distance measurement ucomprising means for transmitting from one point a beam of radiant energy adapted to rotate in azimuth and means yfor receiving said beam at another point for providing an indication of 4distance between said two points, said latter means comprising four independent aerials arranged at the extremities of ltwo distance measuring vbase lines at right angle to each other, means for combining the effects of reception of two aerials forming one base line so as to obtain `a voltage measuring the parallax angle of said base with respect to the point of origin of the rotating beam, means for combining in ya similar manner the eiects of reception of two other aerials forming the other base line and means for combining said two voltages so as to provide an indication of distance as a function of the angle of parallax of a base line of the same length as said base lines placed at the point of reception symmetrically and perpendicularly to a direction passing through said point of reception and said point of transmission `of `the rotating beam.

18. A system for distance measurement comprising means for transmitting synchronously related radiations presenting a variable characteristic, from two points symmetrically disposed at one location on either side of a direction joining said location with another location, and means for receiving said radiations at said other location comprising at least two spaced independent aerials also symmetrically disposed on either side of the direction joining the two locations and means for combining the effects of reception of said aerials to provide an indication of distance between said locations.

19. A system for distance measurement `comprising means for transmitting synchronously related frequency modulated radiations from two points symmetrically disposed at one location on either side of a direction joining said location to another location, and means for receiving said radiations at said other location to provide an indication of distance, said latter means comprising at least two spaced independent aerials also symmetrically arranged on either side of the direction joining the two locations, means for measuring differences of frequencies received by each aerial from both transmitters simultaneously and means for adding up said frequency differences to provide an indication of distance between said two locations,

20. A system for distance measurement ccmprising means for transmitting synchronously related frequency modulated radiations from two points symmetrically disposed at one location on either side of a direction joining said location to another location, and means for receiving said radiations at said other location to provide an indication of distance, said latter means comprising at least two spaced independent aerials also symmetrically arranged on either side of the direction joining the two locations, means for detecting and amplifying the frequency modulated signals received by each aerial, means for transforming said signals into variable amplitude signals and means for adding up said variable amplitude signals derived from the two aerials to provide an indication of distance.

21. A system for distance measurement between a dirigible craft and a desired point on the ground comprising means at said point for transmitting variable characteristic radiations, means on the craft for receiving said radiations comprising at least two aerials placed at the opposite extremities of a base line transversal to said craft, and means for correlating the effects of reception of said radiations by said aerials, as regards to the value of said variable characteristic upon reception of said radiations by the tWo `aerials. r

PIERRE ANDRE PERILHOU.

References Cited in the le of this patent UNITED STATES PATENTS Number Number 20 13,924 108,643

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